Subject: [PATCH v2 5/6] mm/mremap: Allow arch runtime override

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Mon, 15 Mar 2021 17:08:23 +0530

Architectures like ppc64 can only support faster mremap only with radix
translation. Hence allow a runtime check w.r.t support for fast mremap.

Signed-off-by: Aneesh Kumar K.V <[email-masked]>
---
 arch/arc/include/asm/tlb.h     |  5 +++++
 arch/arm64/include/asm/tlb.h   |  6 ++++++
 arch/powerpc/include/asm/tlb.h |  6 ++++++
 arch/x86/include/asm/tlb.h     |  5 +++++
 mm/mremap.c                    | 14 +++++++++++++-
 5 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/arch/arc/include/asm/tlb.h b/arch/arc/include/asm/tlb.h
index 975b35d3738d..22b8cfb46cbf 100644
--- a/arch/arc/include/asm/tlb.h
+++ b/arch/arc/include/asm/tlb.h
@@ -9,4 +9,9 @@
 #include <linux/pagemap.h>
 #include <asm-generic/tlb.h>
 
+#define arch_supports_page_tables_move arch_supports_page_tables_move
+static inline bool arch_supports_page_tables_move(void)
+{
+	return true;
+}
 #endif /* _ASM_ARC_TLB_H */
diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
index 61c97d3b58c7..fe209efc6a10 100644
--- a/arch/arm64/include/asm/tlb.h
+++ b/arch/arm64/include/asm/tlb.h
@@ -94,4 +94,10 @@ static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pudp,
 }
 #endif
 
+#define arch_supports_page_tables_move arch_supports_page_tables_move
+static inline bool arch_supports_page_tables_move(void)
+{
+	return true;
+}
+
 #endif
diff --git a/arch/powerpc/include/asm/tlb.h b/arch/powerpc/include/asm/tlb.h
index 160422a439aa..058918a7cd3c 100644
--- a/arch/powerpc/include/asm/tlb.h
+++ b/arch/powerpc/include/asm/tlb.h
@@ -83,5 +83,11 @@ static inline int mm_is_thread_local(struct mm_struct *mm)
 }
 #endif
 
+#define arch_supports_page_tables_move arch_supports_page_tables_move
+static inline bool arch_supports_page_tables_move(void)
+{
+	return radix_enabled();
+}
+
 #endif /* __KERNEL__ */
 #endif /* __ASM_POWERPC_TLB_H */
diff --git a/arch/x86/include/asm/tlb.h b/arch/x86/include/asm/tlb.h
index 1bfe979bb9bc..62915238bb36 100644
--- a/arch/x86/include/asm/tlb.h
+++ b/arch/x86/include/asm/tlb.h
@@ -37,4 +37,9 @@ static inline void __tlb_remove_table(void *table)
 	free_page_and_swap_cache(table);
 }
 
+#define arch_supports_page_tables_move arch_supports_page_tables_move
+static inline bool arch_supports_page_tables_move(void)
+{
+	return true;
+}
 #endif /* _ASM_X86_TLB_H */
diff --git a/mm/mremap.c b/mm/mremap.c
index fafa73b965d3..316181822cce 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -25,7 +25,7 @@
 #include <linux/userfaultfd_k.h>
 
 #include <asm/cacheflush.h>
-#include <asm/tlbflush.h>
+#include <asm/tlb.h>
 #include <asm/pgalloc.h>
 
 #include "internal.h"
@@ -210,6 +210,14 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
 		drop_rmap_locks(vma);
 }
 
+#ifndef arch_supports_page_tables_move
+#define arch_supports_page_tables_move arch_supports_page_tables_move
+static inline bool arch_supports_page_tables_move(void)
+{
+	return false;
+}
+#endif
+
 #ifdef CONFIG_HAVE_MOVE_PMD
 static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
 		  unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
@@ -219,6 +227,8 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
 	struct mmu_gather tlb;
 	pmd_t pmd;
 
+	if (!arch_supports_page_tables_move())
+		return false;
 	/*
 	 * The destination pmd shouldn't be established, free_pgtables()
 	 * should have released it.
@@ -297,6 +307,8 @@ static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
 	struct mmu_gather tlb;
 	pud_t pud;
 
+	if (!arch_supports_page_tables_move())
+		return false;
 	/*
 	 * The destination pud shouldn't be established, free_pgtables()
 	 * should have released it.
-- 
2.29.2